Grey box testing and double grey box testing are two types of software testing methods that differ in the amount of information that is shared between the testers and the target system.
In grey box testing, the testers have partial knowledge of the internal structure of the system, such as the architecture, the data structures, or the algorithms. They use this information to design test cases that can cover both the functionality and the code of the system. Grey box testing is a combination of black box testing and white box testing, where black box testing does not require any knowledge of the internal structure, and white box testing requires full access to the source code. Grey box testing can provide better test coverage and efficiency than black box testing, as well as identify context-specific errors that are related to web systems.
In double grey box testing, not only the testers have partial knowledge of the internal structure of the system, but also the system has partial knowledge of the test cases that are being executed. This means that the system can adapt its behavior or responses based on the test cases and try to evade or deceive the testers. Double grey box testing is often used in penetration testing or security testing, where the testers try to find vulnerabilities or weaknesses in the system, and the system tries to defend itself or hide its flaws. Double grey box testing can provide a realistic assessment of the security posture and resilience of the system, as well as challenge the skills and creativity of the testers.